PHOENIX -- A billionaire business owner who died along with four others in a 2010 helicopter crash allowed his 5-year-old daughter to sit on his lap in the co-pilot's seat where she apparently kicked the flight controls and caused the accident, according to federal investigators.

The National Transportation Safety Board reviewed the crash that killed Services Group of America founder and owner Thomas J. Stewart, 64, for nearly three years before releasing its final probable cause report this week.

Services Group of America founder Thomas J. StewartAP Photo/Services Group of America

Stewart's young daughter, wife, brother-in-law and company pilot also were killed in the crash on Valentine's Day 2010.

The NTSB found that Stewart allowed his daughter, Sydney, to sit on his lap on a trip from his northern Arizona ranch to his home in Scottsdale, the Phoenix suburb where SGA is headquartered.

It was "highly likely" that the child suddenly pushed down with her foot on the copter's controls, according to the Nov. 7 report. Either Stewart or his pilot then quickly pulled up on the controls, causing the helicopter's main blades to bend and strike the aircraft's tail, the report said.

The helicopter then plunged out of control into a dry stream bed in the north Phoenix community of Cave Creek, killing all aboard instantly, according to investigators.

Madena Stewart, 40, her brother, Malang Abudula, 38, and company pilot Rick Morton, 63, were also killed in the crash.

The report's conclusion was immediately challenged by the lawyer for the pilot's family, who has blamed a faulty rotor blade for the crash, and by Stewart's company.

"That's their interpretation, and it does not comport with what our experienced investigators believe happened," said Gary C. Robb, a Kansas City, Mo., attorney who specializes in aviation accidents.

Robb has sued Eurocopter and others involved in repairing one of the helicopter's blades after a previous mishap. He said he believes the repair was faulty and the blade came apart in flight, causing the crash.

The NTSB found no evidence of that. It concluded that the repaired blade hit the tail rotor drive shaft and broke.

Eurocopter helped the NTSB investigate the crash and ran simulations that concluded that only a rapid down and then up movement on a control called a "collective" could have caused the accident.

"Unfortunately, we believe that Eurocopter had some input into that report, as Eurocopter conducted its own evaluation to exonerate itself," Robb said in an interview with The Associated Press on Friday.

The NTSB laid some blame on the pilot for not controlling his cockpit. For example, it found that Stewart liked to fly the craft even though he wasn't licensed for helicopters. The report faulted Morton for allowing such a violation.

William Waldock, who teaches air crash investigation at Embry-Riddle Aeronautical University in Prescott, Ariz., reviewed the NTSB report and said there is no direct evidence that the child kicked the controls.

"A sudden up and down" movement of the controls would have led to such an accident, Waldock said. But he added that he didn't see "any direct evidence that factually verifies" that the girl kicked the controls.

SGA issued a statement saying the NTSB investigated the crash with Eurocopter but without outside investigators.

"Despite this length of time, there are many questions that remain unanswered, not the least of which is that the NTSB's conclusion is at odds with every single eyewitness," it said.

Also, the statement said, "the conclusion is wholly inconsistent with the way Rick Morton commanded the helicopter and the respect Tom Stewart gave his pilots in the cockpit."

The company said now that the report is public, independent experts will have access to the evidence and "will be able to conduct a more thorough investigation into the cause of the crash. Because the matter is in litigation, the company cannot comment further."

NTSB reports are approved by the agency's board. No one was available to comment on the findings at American Eurocopter's Texas headquarters Saturday.

Stewart joined his father's Seattle-based port support business in the late 1960s and expanded it into insurance and food distribution, fruit packing and retailing.

After spinning off some subsidiaries, he moved the company to Arizona in 2006. It remains privately held.